It is well known that in industrial operation, chains and specifically chain links undergo wear so that the original section thickness of the chain link becomes reduced. Excessive reduction of this original nominal wire diameter renders the chain unsafe so that such a chain or chain link should be removed from service. Various devices have been previously designed for determining the nominal, unworn diametral size of various items such as round stock and drills as exemplified by U.S. Pat. Nos. 1,881,651; 2,981,005; 3,381,385; 1,860,174; and 1,389,486. All of these patents are directed to measuring the unworn nominal size for the purpose of determining the original size of the article as opposed to determining the point at which the nominal size has been unsatisfactorily reduced in dimension.
U.S. Pat. No. 1,638,885 discloses a safety appliance gauge which includes a body of sheet material having slots formed therein for the purpose of determining whether or not certain specific safety related components on railway trains are of less than safe proportions. The slots formed in this gauge, however, have openings which are exactly equal to the dimensions of the respective components to be measured. The inspector using the gauge determines when a measured component has an unacceptably reduced dimension by detecting the existance of play between the two edges of the slots and the measured component. The disclosed apparatus and technique are, however, undesirable in that they require the inspector's judgement since a small degree of play always exists in order to permit the gauge to fit over the measured component in the first instance. Furthermore, the disclosed gauge is not adapted to accommodate or give a measure of the factor of safety which is initially incorporated in all such safety related components. Thus, the technique for using the disclosed gauge does not permit wear of any of the components even though they initially include an initial factor of safety.